The potential energy surface of He-HCN determined by fitting high-resolution spectroscopic data

Two potential energy surfaces for He-HCN are determined by least-squares fitting of parameterised functional forms to data from high-resolution microwave and millimeter-wave spectroscopy [Drucker et al., J. Phys. Chem. 99, 2646 (1995)]. The two potentials both have significantly deeper wells than suggested by the ab initio supermolecule calculations of Drucker et al. Both potentials have linear or near-linear equilibrium geometries, He-H-C-N, but the shapes of the well depth functions away from the linear geometry are significantly different. The existing experimental data are thus not sufficient to probe this potential feature in detail. Predictions of spectroscopic properties that would allow the new potentials to be tested and refined are given. (C) 1996 American Institute of Physics.